[apparmor] [PATCH 4/5] Add the ability to read proc attr interfaces

[John Johansen]

On 07/12/2011 12:01 PM, Seth Arnold wrote:
> The ret=1 just before the for loop isn't needed (except to quiet warnings?) 
> I think the entire for loop would be easier read as a while loop.
> 
heh, sorry you were right, I missed that I was double assigning ret.

revised patch using while and fixing a couple of bugs below

---

Add the ability to read proc attr interfaces

Signed-off-by: John Johansen <john.johansen at canonical.com>

diff --git a/libraries/libapparmor/src/kernel_interface.c b/libraries/libapparmor/src/kernel_interface.c
index 0e61065..9f16bd0 100644
--- a/libraries/libapparmor/src/kernel_interface.c
+++ b/libraries/libapparmor/src/kernel_interface.c
@@ -54,6 +54,68 @@ static char *procattr_path(pid_t pid, const char *attr)
 	return NULL;
 }
 
+/**
+ * getprocattr - get the contents of @attr for @tid into @buf
+ * @tid: tid of task to query
+ * @attr: which /proc/<tid>/current/attr to query
+ * @buf: buffer to store the result in
+ * @len: size of the buffer
+ *
+ * Returns: size of data read or -1 on error, and sets errno
+ */
+static int getprocattr(pid_t tid, const char *attr, char *buf, int len)
+{
+	int rc = -1;
+	int fd, ret;
+	char *ctl = NULL;
+	int size = 0;
+
+	if (!buf || len <= 0) {
+		errno = EINVAL;
+		goto out;
+	}
+
+	ctl = procattr_path(tid, attr);
+	if (!ctl)
+		goto out;
+
+	fd = open(ctl, O_RDONLY);
+	if (fd == -1) {
+		goto out;
+	}
+
+	do {
+		ret = read(fd, buf, len);
+		if (ret <= 0)
+			break;
+		buf += ret;
+		size += ret;
+		len -= ret;
+		if (len < 0) {
+			errno = ENAMETOOLONG;
+			break;
+		}
+	} while (ret > 0);
+
+	if (ret < 0) {
+		int saved;
+		if (ret != -1) {
+			errno = EPROTO;
+		}
+		saved = errno;
+		(void)close(fd);
+		errno = saved;
+		goto out;
+	}
+
+	(void)close(fd);
+
+	rc = size;
+out:
+	free(ctl);
+	return rc;
+}
+
 static int setprocattr(pid_t tid, const char *attr, const char *buf, int len)
 {
 	int rc = -1;